Simply the radical expression
Well, things like sporting events, or freak storms are measured in days, or weeks. Depends. For weather, it could be hurricanes, tornado's, or even large fires(not quite weather, but could be)
A.) R(20) = -10(20)^2 + 800(20) = -10(400) + 16000 = -4000 + 16000 = $12,000
R(25) = -10(25)^2 + 800(25) = -10(625) + 20000 = -6250 + 20000 = $13,750
R(30) = -10(30)^2 + 800(30) = -10(900) + 24000 = -9000 + 24000 = $15,000
b.) For maximum revenue, dR/dp = 0
dR/dp = -20p + 800 = 0
20p = 800
p = 40
Therefore, the maximum revenue will be recorded when the price is set at $40.
Angle ADB is a right angle, which is given.
The measure of ADB is 90 degrees by definition of right angle.
The two angles are a linear pair (aka they're supplementary) by definition of linear pair (they're formed by two intersecting lines).
The measure of BDC is 90 because BDC + ADB = 180 (definition of linear pair), and ADB = 90 (given).
BDC = ADB because 90 = 90
Overall, the two triangles are congruent by SAS.